The starting material for the production of active-mass is lead powder. Lead powder is prepared from lead, e.g. in a Barton mill usually known in industry, and in the course of milling, depending on the grinding conditions, lead oxide is also formed in different amounts. The powder thus obtained is subjected to sulfuric acid/phosphoric acid treatment depending on whether positive or negative active-mass is aimed to be prepared and additives, e.g. sulfuric acid, barium sulfate are mixed to the product thus obtained. The resulting crude active-mass is spread onto electrodes of grid structure with the aid of a spreading machine. Then further operations are carried out on the mass thus applied onto the plates, e.g. pre-drying and aging. In the course of the said operations tetrabasic lead sulfate, wherein the ratio of lead oxide (PbO) to lead sulfate (PbSO.sub.4) is 4:1, is formed in the active-mass.
In the accumulator production it is unavoidable that defective plates are also produced. The need for the re-use of such defective plates and for the use of the active-mass content thereof has arisen for a long time.
There are more solutions in the prior art for solving the above problem. According to the most generally employed metallurgical way the plates dismounted from the defective and used accumulators are melted together with the active-mass and the melting process is optionally repeated. Thus the lead-oxide content of the active mass can be separated from the lead alloy from which the grid is formed. The active mass thus recovered is charged into the mixing machines wherein the active-mass is stirred for repeated use according to U.S. Pat. No. 4,009,833 (lines 25 and 26 of column 2). The efficacy of this process is quite low, its heat-energy demand is high and it can also be objected to from the point of view of health and environment protection.
In the industry the process is also known in which the active-mass content of negative plates is separated from the grid with the aid of water jet and the active mass is recycled into the production. However, this process can be used only in case of negative active mass, i.e. it is not suitable for the re-use of all of the wastes. In addition, the negative plates comprising the active mass thus recovered and the accumulators wherein these plates are built in are of reduced capacity. When the said active mass is used, the quality of spreading is lower than when fresh active mass is used and the spreading of the plates on both side can hardly be solved or cannot be solved.
The greatest disadvantage of this process resides in the treatment of the high amount of waste water, containing lead and lead compounds, both from energy-supply and environment-pollution points of view. Probably owing to these reasons the recycling of waste active mass into active-mass mixing equipments has not been spread in the industry.
When working out the present invention, our aim was to partially or fully eliminate the above-listed drawbacks of the known processes and to provide a process which renders it possible to recycle not only the negative but also the positive active-masses into the production and to utilize the positive and negative active masses of the defective accumulators.
The invention is based on the recognition that if the positive and negative active-mass wastes collected separately and stored under pure conditions are fed into the lead-powder mill, instead of the active-mass mixing equipment, as it was suggested by U.S. Pat. No. 4,009,833, and plates are prepared from the ground material thus obtained, then their properties are better than those of the fresh ones.